Thermal analysis of the volume phase transition with N-isopropylacrylamide gels

Otake, Katsuto; Inomata, Hiroshi; Konno, Mikio; Saito, Shozaburo

doi:10.1021/ma00203a049

Cited by 734 publications

(613 citation statements)

References 22 publications

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“…Conflicting data are reported in the literature concerning the relationships between the phase transition of the linear polymers and the hydrogels. Some authors report that both the transition temperature and the heat of collapse of the poly(NIPAAm) gel show similar values to those of the poly(NIPAAm) solutions [23]. Other authors report that the transition temperature of poly(NIPAAm) gels is slightly higher (1-2ºC) than that of the linear polymer solutions [24,25].…”

Section: Preparation and Characterization Of Thermoresponsive Microspmentioning

confidence: 97%

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

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Abstract. One of the most subtle problem in the characterization of thermoresponsive polymers is the evaluation of the relationship between the lower critical solution temperature (LCST) of the linear polymer and the volume phase transition temperature (VPTT) of the corresponding hydrogel. Here, the LCST and the onset temperature of linear poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) has been determined under pseudo-physiological conditions by cloud point (CP) measurements and by microcalorimetric analysis. The LCSTs, as well as the onset temperatures, determined by the CP method, decrease with increasing the concentration of the polymer solution. On the contrary, microcalorimetric analyses give almost the same values for LCSTs and the onset temperatures regardless of polymer concentration. The VPTT of the hydrogel, determined by the blue dextran method, was found to be closely similar to the LCST of the concentrated polymer solution (10%, w/v), determined by the CP method. In fact, the hydrogel could be considered as a concentrated polymer solution whose concentration could be related to the amount of water retained by the hydrogel. Hydrogel microspheres have been also reported to release diclofenac, a drug model system, in a pulsating way at temperatures slightly below and above the VPTT.

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Section: Preparation and Characterization Of Thermoresponsive Microspmentioning

confidence: 97%

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

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show abstract

“…The bisalkynelinked PNIPAM that was designed as no end-group effect reference gave the smallest molecular weight dependence among the three series studied here. As mentioned above, previous studies of PNIPAM and other thermoresponsive polymers have demonstrated the LCST to be independent [32][33][34]45], directly dependent [10,26], or inversely dependent [17,[27][28][29][30][31]46,47] upon polymer molecular weight. LCSTs are expected to be decreased with increasing molecular weight on the basis of the changes in the polymer-solvent interaction [48,49].…”

Section: Thermoresponsivity Of Pnipams Before and After Click Reactionmentioning

confidence: 79%

“…LCSTs are expected to be decreased with increasing molecular weight on the basis of the changes in the polymer-solvent interaction [48,49]. However, end-groups attached to the chain end can mitigate this trend or perhaps reverse by changing the hydrophobic/hydrophilic nature of the polymer [27,34,44,50].…”

Section: Thermoresponsivity Of Pnipams Before and After Click Reactionmentioning

confidence: 99%

“…However, the end-effect contribution is significantly dependent on the polymer molecular weight as well as its polydispersity [23]. Previous studies have demonstrated that the LCST of PNIPAM with monofunctional end-group was directly dependent [10,27], inversely dependent [28][29][30][31][32], or independent [33][34][35] on the molecular weight of PNIPAM, respectively. These different results may be attributed to different polymer end-groups as well as polydispersity, or different techniques for measuring LCSTs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Well-defined poly(N-isopropylacrylamide) with a bifunctional end-group: synthesis, characterization, and thermoresponsive properties

Liu

Liao

Yang

et al. 2012

Designed Monomers and Polymers

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(2013) Well-defined poly(N-isopropylacrylamide) with a bifunctional end-group: synthesis, characterization, and thermoresponsive properties, Designed Monomers and Polymers, 16:5, 465-474, DOI: 10.1080/15685551.2012 In this study, well-defined poly(N-isopropylacrylamide) (PNIPAM) with a bisalkyne end-group was synthesized by reversible addition-fragmentation chain transfer polymerization using 2-(2-(ethylthiocarbonothioylthio)-2-methylpropanoyl-oxy)ethyl 3,5-bis(prop-2-ynyloxy) benzoate (EMEB) as the chain transfer agent. The molecular weight and polydispersity index of polymer was determined by gel permeation chromatography (GPC). The linear increase in molecular weight with conversion, unimodal, and almost symmetrical peak in GPC trace together with low polydispersity indicated the controlled polymerization process of NIPAM mediated by EMEB. Subsequently, the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition between the end-group of polymer and azide derivatives was carried out to produce PNIPAM, in which the bisfunctional end-group was modified with phenyl, octyl, amido, and hydroxyl groups. After completing the click reaction, the structure of the polymer was characterized carefully by Fourier transform infrared spectroscopy (FTIR), 1 H NMR, and Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), indicating the complete consumption of alkyne end-groups. In addition, almost no change in molecular weight as well as the polydispersity was observed by comparison with the GPC traces of polymers before and after click reaction. The cloud point temperatures (T cp s) of the resulting PNIPAM derivatives in aqueous solution were investigated in detail by dynamic light scattering. The results showed that the values of T cp were ranged from 22 to 38°C, which depended largely on end-groups as well as the polymer molecular weights.

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“…With a change in the temperature, these hydrogels can undergo a phase transition, upon which their volume can discontinuously change by up to 1000 times [23]. For the application of temperature-responsive hydrogels [24][25][26][27][28][29], both good responsive properties and good mechanical properties are necessary to generate desirable forces or deformations.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the bending of bilayer temperature-sensitive hydrogels

Dong

Chen

2017

Proc. R. Soc. A.

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Stimuli-responsive hydrogels can serve as manipulators, including grippers, sensors, etc., where structures can undergo significant bending. Here, a finite-deformation theory is developed to quantify the evolution of the curvature of bilayer temperature-sensitive hydrogels when subjected to a temperature change. Analysis of the theory indicates that there is an optimal thickness ratio to acquire the largest curvature in the bilayer and also suggests that the sign or the magnitude of the curvature can be significantly affected by pre-stretches or small pores in the bilayer. This study may provide important guidelines in fabricating temperature-responsive bilayers with desirable mechanical performance.

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Thermal analysis of the volume phase transition with N-isopropylacrylamide gels

Cited by 734 publications

References 22 publications

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Well-defined poly(N-isopropylacrylamide) with a bifunctional end-group: synthesis, characterization, and thermoresponsive properties

Quantifying the bending of bilayer temperature-sensitive hydrogels

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